The use of low molecular weight ethylene/alphaolefin/nonconjugated diene terpolymers ("EPDM") as caulks and/or sealants has long been proposed by the art. Thus, U.S. Pat. No. 3,819,592 to Visser et al discloses a process for producing low molecular weight ethylene/propylene/(optionally) nonconjugated diene copolymers employing a vanadium salt/alkylaluminum halide catalyst and a molecular weight regulator which is a phosphorodithioate, a dithiocarbamate or a dithiocarbonate. This patent broadly discloses that curable liquid ethylene/alphaolefin/diene terpolymers can be utilized as adhesives, caulking compounds, sealants and plasticizing coagulants. However, Visser et al neither discloses nor suggests any formulations for so employing such low molecular weight terpolymers.
Despite its low molecular weight and "liquid" properties, lower molecular weight EPDM itself generally possesses too high a Brookfield viscosity at ambient temperatures and pumpable shear rates to be employed in pumpable formulations. Thus, for example, EPDM having a molecular weight of only about 7000 typically possesses a Brookfield viscosity of more than 6,000,000 centipoise at room temperature and pumpable shear rates. This viscosity dramatically increases even farther above the desired maximum pumpable Brookfield viscosity of about 5,000,000 centipoise upon the addition of fillers conventionally employed in compositions useful for insulation and/or sealant applications.
Accordingly, in order to lower the viscosity of the formulated composition to thereby produce a pumpable sealant or caulk it is customary to add either relatively large amounts of solvent or a plasticizer to such an EPDM sealant formulation. However, the use of large amounts of solvent is generally undesirable as such solvents will tend to run after the composition has been injected thereby adversely affecting the ability of the sealant compound to completely fill the recesses of the irregularly shaped volumes. In addition, the presence of high solvent levels will result in a high degree of shrinkage of the sealant composition and, provided a blowing agent is present, will tend to result in the production of an undesirable highly nonuniform cellular structure. Moreover, health and/or environment hazards are generally associated with the use of many conventional organic solvents.
Moreover, there are serious drawbacks associated with the use of conventional plasticizers which are generally low molecular weight hydrocarbons such as mineral oils or paraffinic oils. Not only will such conventional plasticizers adversely affect the tensile properties of the resultant cured composition, but the tendency of such oils to migrate from the rubber will greatly interfere with the ability of the compositions to adhere to the substrates (particularly materials such as galvanized metal surfaces) which the sealant is intended to protect.
Accordingly, it is an object of the present invention to provide a sealant, caulking and/or insulation composition which is readily pumpable into irregularly shaped voids.
It is a further object of this invention to provide a sealant, insulation caulking composition which will exhibit increased adhesion to oily galvanized metal surfaces, such as those typically encountered in the automotive industry.
It is yet another object of this invention to provide a process for insulating a substrate (e.g., from heat, air, water and/or sound) employing such a sealant and/or caulking composition.
The above objects and other additional objects will become more fully apparent from the following description and accompanying Examples.